1. Field of the Invention
This invention relates generally to electrical male plugs and in particular to an apparatus for locking electrical male plugs and rendering them temporarily unusable.
2. Description of the Prior Art
Numerous conditions exist where it is imperative that electrical equipment and devices be controlled and only operated at appropriate times for appropriate reasons by appropriate persons. The gambit ranges from the industrial shop equipment to the teenagers' television set. This invention covers this range of electrical devices that are powered by inserting a male electrical plug into female electrical outlet. There are other types and styles of electrical lockout systems for machines and devices that are wired directly to the source of current, however the invention described and claimed herein relates only to those that in effect are plugged in to the wall.
The problem of unauthorized use of electrical devices is not new and attempts have been made in the past for a simple, reliable and effective means to control unauthorized use, thus far the devices proposed fall short of the mark in one fashion or another. For example, U.S. Pat. No. 4,025,140 issued May 24, 1977 to Matys discloses a male plug locking device that uses a housing to enclose the conductors and includes a threaded lock screw to engage the aperture on one conductor. The head of the screw is of a special design and therefore requires a key to match that design to move the screw into and out of the locking position. U.S. Pat. No. 4,957,446 issued Sep. 18, 1990 to Belsky shows another lock out device that utilizes a housing to cover the electrical connectors and then provides a flexible strap that passes through holes in the housing and the connectors. The reusability of the strap is a question in this device. Another U.S. Pat. No. 5,055,057 issued Oct. 8, 1991 to Boyer who discloses a housing adapted to receive a pair of electrical connector prongs and automatically engage the holes in the prongs. The housing remains in place, locking the plug until a key for the housing is inserted and turned withdrawing the locking studs from the connector prongs thereby separating the housing from the prongs. A U.S. Patent granted to Herbert No. 5,176,527 on Jan. 5, 1993 shows a block housing with at least one channel for receiving a projecting portion of an electrical connector. A threaded bore intersects the channel and contains a locking pin that engages the projecting portion of the connector and further includes a second bore intersecting the threaded bore and adapted to receive a means in the nature of a lock that would prevent access to the locking pin. In U.S. Pat. No. 5,277,600 issued Jan. 11, 1994 to Meixler a safety lock is disclosed which includes a plastic block adapted to receive an electrical plug. Holes aligned to accept an ordinary bolt that would pass through the block and the electrical connectors and be locked in place preventing use of the plug.
The devices shown and known to the Applicant all require locks, keys or tools to operate. The one device that does not, is destroyed in the process of removal or uses a lock to avoid destroying the strap lock. The prior art fails to show a male plug lock that will secure the connectors and render the plug unusable with or without a separate lock or key depending upon the application.